The demand for mobile data and voice communication continues to evidence significant growth. Examples for mobile communication systems include cellular-based wireless communication networks. Such networks include various network nodes. The network nodes may include base stations which respectively provide coverage for a radio cell.
A user equipment of a mobile communication network may be a Proximity Service (ProSe) enabled device. Several ProSe enabled user equipments which are located in proximity to each other are operative to perform device-to-device (D2D) communication. D2D communication allows user equipments of a mobile communication network to directly communicate with each other when the user equipments are located in proximity to each other. D2D communication has a wide variety of applications, including public safety and other use cases. Emergency calls are one example for public safety use cases of D2D communication. Direct data or voice communication between user equipments is another example for use cases of D2D communication. For illustration, ProSe enabled user equipments located in proximity to each other may engage in data or voice communication.
In order to perform D2D communication, a user equipment must be capable of detecting one or several other user equipments which are located in proximity to the user equipment.
The resources, e.g. the subcarrier frequencies, slots and/or symbols which the user equipment may use for the D2D discovery may be allocated to the user equipment by a base station. Similarly, the resources, e.g. the subcarrier frequencies, slots and/or symbols which the user equipment may use for the D2D communication may be allocated to the user equipment by a base station. Transmission of data as D2D communication may involve scheduling assignments. A scheduling assignment may be used to determine in which resources, e.g. in which subcarrier frequencies, slots and/or symbols, a user equipment may transmit or receive data.
User equipments may perform D2D discovery and/or D2D communication even when they are located out of coverage of the cellular communication network. The resources for scheduling assignments or data resources may be preconfigured by the cellular communication network. The preconfigured resources available for D2D discovery and/or D2D communication in out-of-coverage scenarios may be limited, inter alia because the preconfigured resources must be in conformity with the radio access network resources of several adjacent cells of a cellular communication network.